Mack Trucks president and CEO Denny Slagle will go behind the scenes at three Mack Truck plants including the one in Lower Macungie Township on the hit CBS series “Undercover Boss” at 9 p.m. Sunday.

According to a CBS press release, Slagle brings the assembly line to a “grinding halt” as he works undercover with Mack employees on the reality show that follows company leaders as they secretly work behind the scenes to gain insight on how their company runs.

For the Emmy-nominated reality show, Slagle works side-by-side with employees at the Macungie Assembly Operations plant in Lower Macungie Township. The plant assembles all the trucks sold in North America and employs about 875 people. In 2010, the plant delivered 13,465 trucks.

Mack Trucks, which moved its headquarters from Allentown to Greensboro, N.C. in 2009, is the second largest manufacturer of heavy-duty trucks in the world.

“I came away from this experience with a deeper understanding of the challenges faced by our front-line employees,” Slagle says in a release. “Mack people live up to the brand’s reputation — they’re tough, genuine, dedicated and reliable. The future truly is bright for this 111-year-old American icon.”

The show follows Slagle, sporting a scruffy beard and moustache and having shed his suit for a black Mack Trucks T-shirt and baseball cap, as he goes undercover as a line-worker and accidently brings Mack’s assembly line to sudden halt. Slagle also works behind the scenes at the Hagerstown, Md., plant that produces all of Mack Trucks’ engines and the Baltimore, Md., distribution center that provides parts to Mack dealers and customers. During the course of the show, Slagle discovers that rumors are rampant among employees that Mack Trucks is moving its operations to Mexico.

Slagle, 56, took over as Mack Trucks CEO in 2008. Before that he was the CEO of Volvo Construction Equipment North America in Asheville, N.C.

“Undercover Boss” debuted in 2009 to 38.7 million viewers and was the most-watched premiere episode of any reality series. Each week the show follows an executive as he or she leaves the corner office for an undercover mission to examine the inner workings of the company. While working alongside employees, executives see the effects that their decisions have on others, where the problems lie within their organizations and get an up-close look at both the good and the bad while discovering the unsung heroes who make their companies run.

Past undercover bosses have included Kim Schaefer, CEO of Great Wolf Lodge, which has 12 indoor water parks including one in Scotrun, Monroe County; Joel Manby, president of Herschend Family Entertainment, the company that runs Adventure Aquarium in Camden, N.J., and Ride the Ducks tours in Philadelphia and Michael Rubin, who heads GSI Commerce, a Montgomery County e-commerce giant.